The present invention is directed to systems and methods for the control of chemical manufacturing processes and, more specifically, to multivariate statistical process analysis systems and methods for the production of melt polycarbonate.
Manufacturing process variables (Xi) such as flows, pressures, concentrations, temperatures, and others have traditionally been subject to statistical process control (SPC) strategies. These SPC strategies, introduced in the 1930""s, include a variety of statistical methods designed to maintain process quality and productivity. The statistical methods focus on a single variable Xi at a time, using univariate controls such as Shewhart charts, cumulative sum charts, and exponentially-weighted moving average charts. Such charts are used to monitor the performance of a process, such as a chemical manufacturing process, over time to verify that the process consistently operates within the production specifications of a given product.
As the number of monitored variables Xi affecting the behavior of a manufacturing process increases, however, univariate SPC methods become inadequate. The application of these techniques in such situations may result in misleading information being presented to a process operator, leading him or her to take unnecessary or erroneous control actions.
An alternative approach is to employ multivariate statistical process analysis (MSPA) methods to extract more relevant information from measured data. MSPA methods provide the staff of a manufacturing plant, for example, with a greater understanding of process performance, allowing them to make sound business decisions. Thus, the application of multivariate methodologies to industrial manufacturing processes has experienced increasing popularity in recent years. For example, MSPA methods have been utilized in emulsion polymerization, low-density continuous polyethylene polymerization, batch polymerization, and pilot-scale penicillin fermentation processes. Similarly, MSPA methods have been utilized to improve the productivity of a titanium dioxide plant, monitor the processing conditions of a nuclear waste storage tank, and control the performance of chromatographic instrumentation.
The application of multivariate statistical analysis methods to industrial process data characterized by a large number of correlated chemical process measurements is the area of process chemometrics. The objectives of process chemometrics include the determination of key process variables, the generation of inference models used to forecast and optimize product quality, the detection and diagnosis of faults and potential process abnormalities, and the overall monitoring of chemical processes to ensure production control. Achieving these goals is often difficult with regard to the production of melt polycarbonate, however, as the determination of key process variables may be an inexact and time consuming process, and accurate and reliable inference models may be difficult to generate.
Thus, the present invention is directed to automated multivariate statistical process analysis systems and methods for the production of melt polycarbonate. These systems and methods allow process variables causing abnormal performance to be detected and identified. As a result, a manufacturing plant staff may better understand process performance and make sound business decisions.
In one embodiment, a computerized system for the production of melt polycarbonate includes a plurality of sensors for obtaining a plurality of measurements relating to a plurality of predetermined process variables, a preprocessor for preprocessing each of the plurality of measurements for multivariate statistical analysis, an identifier for identifying which of the plurality of predetermined process variables affect each of a plurality of predetermined product variables, a correlator for correlating the plurality of predetermined process variables and the plurality of predetermined product variables, a model generator for modeling the relationship between the plurality of predetermined process variables and the plurality of predetermined product variables, and an analyzer for analyzing the plurality of predetermined process variables to predict polymer performance and/or to ensure that the value of each of the plurality of predetermined process variables is within a predetermined range.
In another embodiment, a computerized method for the production of melt polycarbonate includes the steps of obtaining a plurality of measurements relating to a plurality of predetermined process variables, preprocessing each of the plurality of measurements for multivariate statistical analysis, identifying which of the plurality of predetermined process variables affect each of a plurality of predetermined product variables, correlating the plurality of predetermined process variables and the plurality of predetermined product variables, modeling the relationship between the plurality of predetermined process variables and the plurality of predetermined product variables, and analyzing the plurality of predetermined process variables to predict polymer performance and/or to ensure that the value of each of the plurality of predetermined process variables is within a predetermined range.